Implantable neurostimulation systems have proven therapeutic in a wide variety of diseases and disorders. For example, Spinal Cord Stimulation (SCS) techniques, which directly stimulate the spinal cord tissue of the patient, have long been accepted as a therapeutic modality for the treatment of chronic pain syndromes, and the application of spinal cord stimulation has expanded to additional applications, such as angina pectoralis, peripheral vascular disease, and incontinence, among others. Spinal cord stimulation is also a promising option for patients suffering from motor disorders, such as Parkinson's Disease, Dystonia and essential tremor.
An implantable SCS system typically includes one or more electrode-carrying stimulation leads, which are implanted at a stimulation site in proximity to the spinal cord tissue (e.g., the dorsal column) of the patient, and a neurostimulator implanted remotely from the stimulation site, but coupled either directly to the stimulation lead(s) or indirectly to the stimulation lead(s) via a lead extension. The neurostimulation system may further comprise a handheld patient programmer to remotely instruct the neurostimulator to generate electrical stimulation pulses in accordance with selected stimulation parameters. The handheld programmer may, itself, be programmed by a technician attending the patient, for example, by using a Clinician's Programmer (CP), which typically includes a general purpose computer, such as a laptop, with a programming software package installed thereon.
Thus, programmed electrical pulses can be delivered from the neurostimulator to the stimulation lead(s) to stimulate or activate a volume of the spinal cord tissue. In particular, electrical stimulation energy conveyed to the electrodes creates an electrical field, which when strong enough, depolarizes (or “stimulates”) the neural fibers within the spinal cord beyond a threshold level, thereby inducing the firing of action potentials (APs) that propagate along the neural fibers to provide the desired efficacious therapy to the patient.
As briefly discussed above, SCS may be to treat patients suffering from motor disorders. Symptoms of motor disorders may be the result of control issues driven by sensory input. A patient with a motor disorder may have a healthy motor cortex, but the input to the motor cortex may be inappropriate. An imbalance between excitatory and inhibitory input into the motor cortex may result in motor disorder symptoms, such as tremor, bradykinesia, abnormal gait, akinesia, and the like. Sensory input travels to the motor cortex via sensory nerves in the dorsal column. Thus, in an effort to restore balance between the excitatory and inhibitory inputs into the motor cortex, stimulation is applied to the dorsal column of the spinal cord in conventional SCS treatments for motor disorders. In order to apply stimulation to the dorsal column 102, the stimulation lead 12 is positioned in the dorsal region 122 of the epidural space 120, as shown in cross-section in FIG. 1. Such dorsal column stimulation for treating symptoms of motor disorders has not yet found widespread use, however, because long-term efficacy in a large number of patients has not been demonstrated. Anecdotal successes have been observed with dorsal column stimulation for motor disorders, but there have been patients who have received no demonstrable benefit. Since SCS is a minimally-invasive approach, SCS techniques for effectively managing symptoms of motor disorders remain attractive in comparison to brain-stimulation-based methods such as Motor Cortex Stimulation or Deep Brain Stimulation.